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        Introduction
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            <h2 class="title"><a id="intro"></a>Chapter 1. 
        Introduction
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          <b>Table of Contents</b>
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            <span class="sect1">
              <a href="intro.html#features">Features</a>
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              <a href="developing.html">Developing a DB Collections Application</a>
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      <p>
        The DB Java Collections API is a Java framework that extends
        the well known 
        <a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/guide/collections/" target="_top">Java Collections</a>
        design pattern such that collections can now be
        stored, updated and queried in a transactional manner. The
        DB Java Collections API is a layer on top of DB.
    </p>
      <p>
        Together the DB Java Collections API and Berkeley DB  provide an
        embedded data management solution with all the benefits of a full
        transactional storage and the simplicity of a well known Java API.
        Java programmers who need fast, scalable, transactional data
        management for their projects can quickly adopt and deploy the 
        DB Java Collections API with confidence.
    </p>
      <p>
        This framework was first known as 
        <a class="ulink" href="http://greybird-db.sourceforge.net/" target="_top">Greybird DB</a>
        written by Mark Hayes. Mark collaborated with us to
        permanently incorporate his excellent work into our distribution
        and to support it as an ongoing part of Berkeley DB and Berkeley DB Java
        Edition. The repository of source code that remains at SourceForge at version 0.9.0 is
        considered the last version before incorporation and will remain
        intact but will not be updated to reflect changes made as part of
        Berkeley DB or Berkeley DB Java Edition.
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              <h2 class="title" style="clear: both"><a id="features"></a>Features</h2>
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        <p>
        <span>Berkeley DB has always provided a Java API which can be roughly
        described as a map and cursor interface, where the keys and values
        are represented as byte arrays. This API is a Java (JNI) interface
        to the C API and it closely modeled the Berkeley DB C API's
        interface.</span> 
        
         

        The DB Java Collections API is a layer on top of 

        <span>that
        thin JNI mapping of the C API to Berkeley DB.</span>

        
        It adds significant new functionality in several ways.
    </p>
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            <li>
              <p>
                An implementation of the Java Collections interfaces (Map,
                SortedMap, Set, SortedSet, 
                <span>List</span> 
                and Iterator) is provided.
            </p>
            </li>
            <li>
              <p>
                Transactions are supported using the conventional Java
                transaction-per-thread model, where the current transaction is
                implicitly associated with the current thread.
            </p>
            </li>
            <li>
              <p>
                Transaction runner utilities are provided that automatically
                perform transaction retry and exception handling.
            </p>
            </li>
            <li>
              <p>
                Keys and values are represented as Java objects rather than
                byte arrays. Bindings are used to map between Java objects and the
                stored byte arrays.
            </p>
            </li>
            <li>
              <p>
                The tuple data format is provided as the simplest data
                representation, and is useful for keys as well as simple compact
                values.
            </p>
            </li>
            <li>
              <p>
                The serial data format is provided for storing arbitrary Java
                objects without writing custom binding code. Java serialization is
                extended to store the class descriptions separately, making the
                data records much more compact than with standard Java
                serialization.
            </p>
            </li>
            <li>
              <p>
                Custom data formats and bindings can be easily added. XML data
                format and XML bindings could easily be created using this feature,
                for example.
            </p>
            </li>
            <li>
              <p>
                The DB Java Collections API insulates the application
                from minor differences in the use of the Berkeley DB Data Store,
                Concurrent Data Store, and Transactional Data Store products.
                This allows for development with one and deployment with another
                without significant changes to code.
            </p>
            </li>
          </ul>
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        <p>
        Note that the DB Java Collections API does not support caching
        of programming language objects nor does it keep track of their stored
        status. This is in contrast to "persistent object" approaches such
        as those defined by 
        <a class="ulink" href="http://www.odmg.org/odmg.html" target="_top">ODMG</a>
        and JDO
        (<a class="ulink" href="http://www.jcp.org/en/jsr/detail?id=12" target="_top">JSR 12</a>).
        Such approaches have benefits but also require sophisticated object
        caching. For simplicity the DB Java Collections API treats data
        objects by value, not by reference, and does not perform object
        caching of any kind. Since the DB Java Collections API is a thin
        layer, its reliability and performance characteristics are roughly
        equivalent to those of Berkeley DB, and database tuning is
        accomplished in the same way as for any Berkeley DB database.
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